1. Field of the Invention
This invention relates to a process for picking up a load from a stack in a load handling apparatus, or the like by which the load stacked on a pallet, or the like is picked up from a layer or layers of its stack, and transferred to another place.
2. Prior Art
It is sometimes necessary that a load stacked in layers, for example, on a pallet be transferred layer by layer onto another pallet.
In a factory producing canned drinks, for example, it is usual to stack corrugated cardboard boxes containing canned drinks on different pallets used for different kinds of drinks, pick up a layer or layers of boxes from one or more of those pallets, and stack them again on different pallets classified by customers.
An apparatus which has been proposed for performing such load handling efficiently is shown in FIG. 6.
The apparatus comprises an unloading lift 50 carrying a load W stacked in layers, a loading lift 51 juxtaposed to the lift 50, and a table 52 reciprocating above and between the lifts 50 and 51. The reciprocating table 52 is provided with a multiplicity of carriage rollers 53 and top carriage rollers 54.
The unloading lift 50 is first raised until the uppermost layer of the load W on the lift 50 is detected by a load height detector 56, as shown by chain lines in FIG. 6a, whereupon the lift 50 stops. Then, the reciprocating table 52 is advanced, while the top carriage rollers 54 are rotated upwardly as shown by an arrow a. The top carriage rollers 54 contact the adjacent side of the load W and pick it up friction for transfer onto the carriage rollers 53. The load W to be picked up is supported by a stopper 55 so as to stay in an orderly position, as shown in FIG. 6b.
The height of the load height detector 56 is so set that the bottom of the uppermost layer of the load W may be at a level which is lower than the top carriage rollers 54 by a certain height .DELTA.D. If the height .DELTA.D is too large, the top carriage rollers 54 fail to perform a proper picking action, and if it is too small, the top carriage rollers 54 engage the second heighest layer of the load W and fail to perform any proper picking action. It is, therefore, necessary for the height .DELTA.D to be set accurately.
The apparatus as hereinabove described cannot, however, recognize any erroneous supply by the lift 50 of pieces of a load W which are differently sized from the intended ones. Therefore, it starts a picking operation, even though the difference in height between the bottom of the uppermost layer of the load W and the top carriage rollers 54 may greatly differ from the set height .DELTA.D. This results in the failure of the apparatus to pick up the load and even the occurrence of damage to the load W or the apparatus.
Even if the load W may be an intended one, the apparatus cannot always be expected to perform a smooth picking up operation, since the individual components of the load W are likely to differ from one another in real height, particularly if they are corrugated cardboard boxes.